Where a quick opening valve is used on compressed gas containers, there is rapid pressure buildup downstream which results in a compression of the gas and an undesirable and oft times dangerous temperature increase. The compression of the gas may also be caused by a sudden closure of a shutoff valve downstream of the controlled process. In the event that oxygen is the gas being used, the resulting adiabatic compression could create an explosive condition should there be any grease or foreign material present in the oxygen chamber.
One attempted solution to the problem is shown in U.S. Pat. No. 2,864,400 to H. P. Wiegel, which shows a double cutoff assembly. In the closed position, the force of both valves in series is transmitted to the valve seat. The main valve is operated manually, discharging gas through an orifice. When the main valve is opened, the auxiliary valve responds to the downstream conditions resulting from the discharge of gas through the orifice. Once sufficient pressure is built up in the discharge nozzle, the auxiliary valve will be forced open, and the gas will discharge at full volume.
However, in U.S. Pat. No. 2,864,400, until the nozzle pressure is sufficient to open the auxiliary valve, flow is permitted solely through the orifice and consequently restricted by the reduced orifice area. Thus, there exists a range of unattainable pressures from the time the initial flow is initiated until the auxiliary valve is unseated.
An alternative valve arrangement is shown in U.S. Pat. No. 824,425 to C. H. Johnson which shows a cylindrical valve assembly at an intermediate position on a fluid line which is responsive to the pressure differential in the line caused by a downstream motor. The tapered valve chamber houses a spring-urged piston valve. When downstream pressure is increased, the piston is urged against the inlet flow affording a maximum passageway for the inlet fluid around the periphery of the piston valve. When downstream pressure is decreased, the incoming fluid will overcome the spring force, urging the spring in the direction of flow and restricting the aforementioned passageway. If the pressure differential is great enough, the peripheral flow around the piston may be entirely cut off. A bleeder port extends through the valve assembly so that fluid flow in the line is not completely obstructed.
The present invention is directed to overcoming one or more of the problems as set forth above.